Sinker (or weight) bars add weight to the tool string to overcome well bore pressure and pull the tool string into the well. Sinker bars help to keep the rod string in tension by providing extra weight. Sinker bars counteract the high hydraulic pressures at the bottom of the tubing. The lower portion of the sucker rod string is forced upward and can be compressed. The compression can cause the sucker rod string to bend. Sinker bars also help prevent the rubbing of the sucker rods on the well bore because the weight holds the sucker rod string in tension.
It would therefore be advantageous to have a sinker bar with greater stability and easier make-up. Faster make-up of the strings of sinker bars takes less time and is more efficient.